Consumption of noncarbonated fruit and vegetable juices has greatly increased since 1950 due to technological breakthroughs in the juice processing and concentration industry. Methods of eliminating sediment, flash pasteurization, concentrating, freeze concentrating, blending, freezing, and drying or crystallization all contributed to this phenomenal growth by providing better quality, better tasting and higher purity juice products which are more convenient to use.
The challenge of producing beverages which are acceptable to a broad range of consumers involves making a unique product having an acceptable flavor, distinctive aroma, acceptable appearance and satisfactory mouthfeel. The aroma and flavor ingredients and the level of pectin in beverages affect each of these characteristics.
During the process of concentrating beverages, especially those involving evaporation, a significant portion of the aroma and flavor volatiles are removed with the water vapors. These volatiles consist of various alcohols, esters, aldehydes, ketones, acids, etc. This loss results in a significant deterioration in quality and overall flavor of the concentrated beverage.
Evaporation processes involve heating the beverage under conditions which promote hydrolysis and/or oxidation of components of the beverage. This causes chemical alterations of the aroma and flavor compounds as well as other materials. For instance, lipids can be oxidized and the amino acids and sugars can undergo browning reactions. Such degradation products can cause off flavors in the concentrated beverage. Thus, conventional evaporation processes frequently result in off-flavors and flavor loss in the juice product produced. Pectin and pulp in the beverage adsorb aroma and flavor components which also contributes to lower display of aroma and flavor levels.
Numerous methods have been devised to compensate for the loss of aroma and flavor during evaporation concentration processes. For instance, U.S. Pat. No. 4,463,025, Strobel, issued Jul. 31, 1984, discloses a process for preparing a fruit juice concentrate prepared from natural citrus fruit ingredients. This process involves freeze concentration. The citrus fruit juice concentrate has at least 35% solids including pulp, non-volatile compounds, pectin and volatile compounds. This citrus fruit juice concentrate has at least 65% of the aroma and flavor volatile compounds of the natural juice. (See also U.S. Pat. No. 4,374,865 to Strobel (1983), which claims a concentrated orange juice).
U.S. Pat. No. 3,248,233 Brent et al., issued Apr. 26, 1966, discloses a method of minimizing the overall loss of aroma and flavor compounds by collecting "essence" of the juice. Essence is the term applied to the first 15% to 20% of the water which is removed through evaporation and which contains a significant amount of volatile aroma and flavor compounds. The escaping essence is condensed, the aroma and flavor compounds recovered and rectified as water is removed, and then added back to concentrated juice. U.S. Pat. No. 3,140,187 Brent, et al, issued Jul. 7, 1964, discloses a juice concentration method.
U.S. Pat. No. 3,118,776, Byer et al., issued Jan. 21, 1964, discloses a multi-step process for recovering the volatile flavor fraction from fruit juices at temperatures of less than 120.degree. F. (49.degree. C.). In a closed system, a thin continuous film of citrus juice is distributed over a heat exchange surface at a substantially reduced pressure to partially concentrate the juice by separating it into two components. The minor fraction containing the aroma and flavor volatiles is condensed and removed. After another separation, the remaining mixture is distilled at a temperature below 100.degree. F. (38.degree. C.) and a pressure of less than 1.5 inches mercury (57.5 mm Hg).
U.S. Pat. No. 2,641,550,Dykstra et al, issued Jun. 9, 1953, discloses the removal of volatiles from orange juice via heating, evaporating under vacuum or by stripping with an inert gas, e.g., nitrogen. Three condensers are used to condense the vapors. The first-stage condenser is maintained at 32.degree. F. (0.degree. C.) to 85.degree. F. (29.degree. C.); 90% to 98% of the distillate is removed. This first fraction is discarded. The second stage condenser is maintained at 32.degree. F. (0.degree. C.) to -95.degree. F. (-139.degree. C.), while the third stage condenser is maintained below -130.degree. F. (-202.degree. C.). The distillates recovered from the second and third stage condensers are later added to the orange juice concentrate.
Each of these procedures is not totally satisfactory because only a fraction of the escaping aroma and flavor volatile compounds can be collected and recovered. Thus, there is necessarily a significant loss in the overall aroma and flavor of the final concentrated product.
Others have tried different procedures for adding back certain volatile compounds and essences to concentrated beverages to enhance the overall flavor and consumer acceptability of the juice. For example, Ahmed et al, J. Agri. Food Chemistry, 26.2, 368-372 (1978), describe the addition of certain volatile compounds and essences to juice concentrate after their recovery from the evaporator. The objective was to match the aroma and flavor found in fresh orange juice.
It is generally recognized that while evaporation concentration processes are useful and fairly effective, there is still a significant loss of aroma and flavor compounds which occurs.
Freeze concentration equipment provides an alternative to the use of evaporators. In freeze concentrators the objective is to remove water in the form of ice crystals without removing significant amounts of aroma and flavor volatiles. However, while freeze-concentration may be satisfactory to achieve aroma/flavor retention during water removal, it is not a desirable procedure for processing fruit with undesirable aroma and flavor characteristics such as those found in green fruit. Moreover, freeze concentration plants require significantly more capital investment than plants based on evaporation techniques.
Fruit juices also contain pectin and methoxylated pectins. Pectins are polycarbohydrate materials which are linked through a glycoside or galactoside linkage. The pectins form a "cloud" in the beverage, making it opaque and viscous. Pectins can be removed by filtration and by hydrolyzing them to make them smaller units of glycocidic linkages. A pectinase enzyme is used to hydrolyze pectin. However, many pectinases also contain enzymes that hydrolyze esters in order to hydrolyze the methyl esters of methylpectins. This removes some of the methyl esters from the pectin thus reducing steric hindrance so that more of the pectin can be depolymerized. However, the removal of these methoxy groups creates methanol in the beverage. In addition, since these esterases are nonspecific and hydrolyze any ester linkage, they may also hydrolyze the important aroma and flavor volatile esters.
The hydrolysis of pectins in fruit juices and fruit puree by using pectinases is known.
Food Engineering, (Jul. 1987) Cloud Stable Vegetable Purees with New Enzymes" describes the advantage of Rohapect.RTM. Mac, a pectinase, as lowering the mass viscosity of purees for easier pressing and producing higher juice yields.
Canadian Patent No. 1,243,890 issued to Beveridge, et al (1988) describes a process for producing light colored fruit juices from apples or pears. A fruit puree which has been heated to destroy color contaminating enzymes is treated with a pectinase and a cellobiase enzyme containing composition. This produces a clear juice. A pectinase enzyme was used on apple puree before the fruit was treated with cellobiase.
EP 298,954 issued to Birkner, et al (1989) discloses the use of immobilized amylase and pectinase to treat juices.
It has been found that it is important to remove pectins, particularly in apple juice, not only because pectins make the juice opaque and viscous but because lowering the pectin levels increases the flavor display and improves the mouthfeel of the juice. This adds significantly to consumer acceptance. Decrease of the pectin level is achieved herein without the formation of methanol and essentially without the hydrolysis of important aroma esters. Thus the integrity of the juice aroma and flavor is retained even though the juice is processed.
Therefore, it is an object of this invention to produce an apple juice which is less viscous by hydrolyzing the pectins using pectinases which are substantially free of esterase activity. This produces a cloudy or clear beverage with decreased viscosity and improved mouth feel with increased aroma and flavor display. The increase in flavor is due to: (1) maintaining the integrity of the aroma and flavor esters and (2) decreasing the adsorption sites of the pectin, i.e. keeping more aroma and flavor materials available for tasting and smelling. This invention produces a clear juice after ultrafiltration of the special enzyme treated juice without further degrading the remaining highly esterified pectins. This juice is not contaminated with copious quantities of methanol.
It is a further object of the present invention to provide a process for producing a less viscous, cloudy or clear beverage or beverage concentrate which contains at least 75%, and in some instances as much as 90% or more of the aroma and flavor volatiles present immediately after extraction of the juice. This present invention also provides a process that is capable of removing the undesirable aroma and flavor components from fruit and vegetable juices without attacking the dissolved solids (e.g. sugars, amino acids, vitamins, phenolic materials, etc.) in the juices.
It is still a further object of this invention to instantaneously separate the desirable aroma and flavor components from fruit and vegetable juices without damaging the dissolved solids and to recapture these aroma and flavor volatiles for addition back to the concentrated fruit and/or vegetable juice.
It is still a further object of this invention to provide a means for pasteurizing a juice beverage before the separation of the aroma and flavor components.
It is also an object of this invention to remove substantially all of the oxygen from a juice beverage in order to prevent flavor degradation due to caramelization of the sugar, browning reactions, oxidation of phenolic and lipid components, and other chemical oxidation reactions of the aroma and flavor volatiles.
These and other objects of this invention will become apparent by the description of the invention below.